Characterization of melA: a gene encoding melanin biosynthesis from the marine bacterium Shewanella colwelliana.

A recombinant plasmid with the ability to impart melanin synthesis to an Escherichia coli host was isolated from a Shewanella colwelliana genomic library. The genetic determinant of the Mel+ phenotype is carried on a 1.3-kb DNA fragment and sequence analysis of this revealed a single intact open reading frame that was sufficient for melanin synthesis (mel). This gene is expressed as a monocistronic transcript and a putative transcription start point is located 115 nucleotides upstream from the translational start codon. The mel gene encoded a protein of 39.5 kDa [346 amino acids (aa)] that showed no aa sequence homology with other proteins known to mediate melanin synthesis (e.g., tyrosinases).